The present invention relates to a fuel supply system for raising a pressure of a fuel and supplying the fuel from a fuel tank to an internal-combustion engine or the like and, more particularly, to a fuel supply system that is prevented from influence of flash produced at the time of forming a housing including fuel passages by welding resin materials.
FIGS. 4 and 5 show a conventional fuel supply system disclosed in the International Publication No. WO96/23967. FIG. 4 is a sectional side view, and FIG. 5 is a plan view. FIG. 6 is an explanatory view of hot plate welding for forming a housing, and FIG. 7 is a sectional view taken along the line X-Y-Z.
In the drawings, numeral 1 is a fuel tank, and numeral 2 is an opening of the fuel tank 1. A lid 3 made of a synthetic resin is formed so as to cover the opening 2, and a sealing gasket 4 is interposed between the lid 3 and the fuel tank 1.
A fuel pump 5, a fuel filter 6, a pressure regulator 7, a fuel level gauge 8, an electric connector 9, and a discharge pipe 10 respectively serving as functional parts of a fuel supply system are integrally built in the lid 3 forming a unit.
The fuel filter 6 is constructed such that a filtration element 12 is accommodated in a housing 11. Moreover, the lid 3 is a part of the housing 11, and the fuel filter 6 is suspended from the lid 3. The housing 11 is comprised of the lid 3 serving as an upper housing and a lower housing 13, and the lower housing 13 is molded of a synthetic resin material. the lid 3 and the lower housing 13 are welded fluid-tight at a boundary portion 14 over the whole circumference, and the filtration element 12 is disposed in the internal space.
An intake pipe 15 serving as a fuel intake port is formed at an upper part on the inner circumferential side of the housing 11 of the fuel filter 6 and is connected to a discharge pipe of the fuel pump 5.
A pipe 16 (indicated by the one-dot chain line in FIG. 4) forming a first fuel discharge port, among two fuel discharge ports of the housing 11, communicates to the discharge pipe 10 provided on the lid 3 and extends upward from a lower end of the lower housing 13.
A return pipe 18 serving as a second fuel discharge port is formed at a lower portion of the lower housing 13 and is connected to the pressure regulator 7.
The electric connector 8 integrally formed with the lid 3 is connected to a power source and a controller (not shown) outside of the fuel tank 1. In the fuel tank 1, the electric connector 8 is connected to the fuel pump 5 through a lead wire not shown, and supplies an electric power to a motor of the fuel pump 5. Further, the electric connector 8 is connected to the fuel level gauge 8 (shown in FIG. 8) through a lead wire not shown and transmits an electric signal indicating a level of the fuel.
The lower housing 13 is made of a conductive synthetic resin and discharges static electricity generated when the fuel passes through the filtration element 12 through the electric connector 8.
In the fuel supply system of above construction, when an electric power is supplied to the fuel pump 5 through the electric connector 8, the fuel pump 5 sucks the fuel through a filter 19, raises a pressure of the fuel, and delivers the fuel to the intake pipe 15 located at the upper part on the inner circumferential side of the housing 11.
The fuel flows through a passage 20 between the lower housing 13 and the lid 3 in the direction indicated by the arrow A. In the fuel filter 6, the fuel flows downwards in the housing 11, whereby dust or the like in the fuel is filtered during the passage of the fuel through the filtration element 12.
The fuel having passed through the filtration element 12, further passing through the discharge pipe 10, is supplied from the pipe 16 to an injector (not shown) of an engine fuel injection system. In this process, the pressure regulator 7 regulates the pressure of the fuel supplied to the injector so that the pressure may be constant, and a surplus fuel generated due to the change in consumption amount is returned from the pressure regulator 7 to the fuel tank 1.
In the mentioned construction, the lid 3 and the lower housing 13 are welded fluid-tight at the boundary portion 14 over the whole circumference, and hot plate welding is generally employed for the welding. In the hot plate welding, as shown in FIG. 6, end faces of the lower housing 13 and the lid 3 to be welded are heated to a melting temperature with a heating plate 30 as a heating source. Then the heating plate 30 is removed, and the joining end faces of the lower housing 13 and the lid 3 are pressed to each other and heat-welded.
In the cross section of the welded portion formed by the hot plate welding, as shown in FIG. 7, an end portion of the molten portion is pushed out due to the pressing and forms a flash 21. The flash 21 varies in size and shape depending upon the state of melting of the joining end faces and the amount of the portion moved due to the pressing. As a result, the housing 11 varies in length. The flash 21 protruding at a portion serving as a fuel passage makes the passage area narrow and increases resistance of the passage. At the same time, pulsation in the fuel flow applies a deformation stress to the flash 21, and a weak portion in the flash 21 sometimes drops due to fatigue fracture. If the flash 21 in a welded portion located upstream from the filtration element 12 of the fuel filter drops, the flash 21 is caught by the filtration element 12. However, if the flash 21 at the welded portion downstream the filtration element 12 comes to drop, there arise such problems as shortage in fuel supply due to clogging of a downstream pipe or engine trouble due to clogging of a nozzle portion of the injector disposed downstream.
The present invention was made to solve the above-discussed problems and has an object of providing a fuel supply system in which the housing is restrained from variation in longitudinal dimensions due to hot plate welding, the flash does not protrude into the passage, and even if any flash of the welded portion drops, the dropped flash does not flow into the passage.
In the fuel supply system according to the invention, for forming a passage for liquid fuel supplied from a fuel pump in a housing, the housing is formed fluid-tight by heat welding joining end faces of an upper housing and a lower housing both made of a synthetic resin, the upper housing and the lower housing are respectively provided with contact ribs facing each other at a tier lower down from the joining end faces, and the joining end faces are subject to melting, pressing and heat welding so that the contact ribs of the upper housing and the lower housing may come in contact with each other.
The contact ribs are provided with space grooves interposed along the joining end faces, the space grooves being formed into a closed staying space at the time of completing the heat welding, and flash getting out at the time of heat welding is caused to stay in the staying space.
The staying space formed by the contact ribs is provided at least in a passage downstream a filtration element.